ML25237A016
| ML25237A016 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 08/27/2025 |
| From: | James Drake Plant Licensing Branch IV |
| To: | Entergy Operations |
| Drake, Jason | |
| References | |
| EPID L-2017-LRO-0064 | |
| Download: ML25237A016 (1) | |
Text
August 27, 2025 Site Vice President Entergy Operations, Inc.
Waterford Steam Electric Station, Unit 3 17265 River Road Killona, LA 70057-3093
SUBJECT:
WATERFORD STEAM ELECTRIC STATION, UNIT 3 - REVIEW OF THE FALL 2023 REFUELING OUTAGE 25 STEAM GENERATOR TUBE INSPECTION REPORT (EPID L-2024-LRO-0035)
Dear Sir or Madam:
By letter dated July 22, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No.ML24204A270), as supplemented by letter dated February 11, 2025 (ML25042A396), Entergy Operations, Inc. (the licensee), submitted information summarizing the results of the fall 2023 steam generator tube inspections performed at Waterford Steam Electric Station, Unit 3 (Waterford 3), during refueling outage 25.
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the information provided and concludes that the licensee provided the information required by the Waterford 3 technical specifications and that no additional followup is required at this time. The NRC staffs review summary is enclosed.
If you have any questions, please contact me at 301-415-8378 or via email at Jason.Drake@nrc.gov.
Sincerely,
/RA/
Jason J. Drake, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-382
Enclosure:
Review of the Steam Generator Tube Inspection Report cc: Listserv
Enclosure REVIEW OF THE FALL 2023 REFUELING OUTAGE 25 STEAM GENERATOR TUBE INSPECTION REPORT ENTERGY OPERATIONS, INC.
WATERFORD STEAM ELECTRIC STATION, UNIT 3 DOCKET NO. 50-382 By letter dated July 22, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24204A270), as supplemented by letter dated February 11, 2025 (ML25042A396), Entergy Operations, Inc. (the licensee), submitted information summarizing the results of the fall 2023 steam generator (SG) tube inspections performed at Waterford Steam Electric Station, Unit 3 (Waterford 3), during refueling outage 25 (RFO 25).
Waterford 3 has two Westinghouse Delta 110 SGs that were installed in 2013. Each SG contains 8,968 thermally treated Alloy 690 tubes with a nominal outside diameter of 0.75 inches and nominal wall thicknesses of 0.044 inches (for rows 1 and 2) and 0.043 inches for the remaining rows. The tubes are hydraulically expanded at both ends for the full depth of the tubesheet and are supported by eight stainless steel tube support plates (TSPs) with trefoil-shaped holes arranged on a triangular pitch. Five sets of anti-vibration bars provide support for the U-bend region of the tube bundle.
The licensee provided the scope, extent, methods, and results of their SG tube inspections in its letter dated July 22, 2024, as supplemented. In addition, the licensee described corrective actions, such as tube plugging, taken in response to the inspection findings.
After reviewing the information provided by the licensee, the U.S. Nuclear Regulatory Commission (NRC) staff has the following observations:
During RFO 25, in situ pressure testing was required for four tubes in SG31, because these four tubes contained nine TSP wear indications that failed to meet the condition monitoring (CM) criteria analytically. Two tubes passed the in situ pressure testing, and two tubes failed the in situ pressure testing. All other wear flaws in SG31 and SG32 satisfied the CM criteria analytically for structural integrity.
The investigation into the TSP wear that exceeded the CM limits showed there was a sub-population of TSP wear indications in rows 1 and 2 of SG31 that should have been accounted for as a separate population in the operational assessment (OA) performed after RFO 21 (spring 2017). This row 1 and 2 sub-population had a higher growth rate than the TSP wear in rows 3 and higher. By treating all TSP wear as a single population, the higher growth rate in rows 1 and 2 was masked by the larger population of TSP wear with a lower growth rate in rows 3 and higher. After RFO 25, an OA was used that divided the SG31 TSP wear into two sub-populations.
The investigation also determined that an erroneous TSP wear flaw sizing curve was used during the RFO 21 inspection that resulted in non-conservative sizing for the TSP wear flaw depths (i.e., the flaws were deeper than measured). The undersized wear flaw data were part of the input used to revise the RFO 21 OA to support an additional cycle of operation before the next SG tube inspection (i.e., moving the SG tube inspection from RFO 24 to RFO 25). To determine whether there were any additional units impacted by an erroneous sizing curve, the eddy current vendor reviewed all prior SG tube inspections performed for the preceding 8-year period and determined that Waterford 3 was the only plant that had applied a non-conservative user-defined eddy current calibration curve.
Additional information regarding the loss of tube integrity is contained in the Waterford 3
- Notice of Violation; NRC Inspection Report 05000382/2024013, dated August 20, 2024 (ML24228A261), and in the Licensee Event Report 50-382/2023-003-00, Steam Generator Tube Degradation Indicated by Failed InSite Pressure Testing Waterford Steam Electric Station, dated December 30, 2023 (ML23364A001).
Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by their technical specifications. In addition, the staff concludes that there are no technical issues that warrant additional follow-up action at this time, since the inspections appear to be consistent with the objective of detecting potential tube degradation and the inspection results appear to be consistent with industry operating experience at similarly designed and operated units, now that the sub-population of TSP wear with the higher growth rate has been accounted for in the most recent OA.
- via eConcurrence NRR-106 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA NRR/DNRL/NCSG/BC NAME JDrake PBlechman SBloom DATE 8/22/2025 8/25/2025 8/25/2025 OFFICE NRR/DORL/LPL/BC NRR/DORL/LPL4/PM NAME TNakanishi JDrake DATE 8/25/2025 8/27/2025